In recent years, studies have been conducted about an ad hoc network in which a plurality of communication apparatuses (hereinafter, referred to as node apparatuses) are mutually connected in an autonomously-distributed manner. Each node apparatus in an ad hoc network autonomously establishes a network according to the communication environment.
Specifically, in an ad hoc network, no access points are provided, and each node apparatus relays a data frame received from a node apparatus that is adjacent to it (hereinafter, referred to as an adjacent node apparatus) to another adjacent apparatus according to the network topology, to deliver the data frame to the apparatus which is the final destination (hereinafter, referred to as the final destination apparatus) such as a gateway apparatus (hereinafter, referred to as a GW apparatus).
At this time, each node apparatus selects a route according to a route cost CRoute and transmits the data frame. That is, when there are a plurality of routes to the final destination apparatus, selection of a route by each node apparatus depends on the definition of the route cost CRoute.
When there is a change in the quality of a link (hereinafter, referred to as the link quality) on a route and the route is changed, a loop route may appear in some cases. A loop route is eliminated when a Hello frame is propagated and the deterioration in the link quality is reported to each node apparatus.
As described above, a loop route in an ad hoc network appears with a change of the route as a trigger, and is eliminated when a Hello frame is propagated and a route is formed again.
However, in an environment with large fluctuations in the link quality, route changes occur frequently. In this case, many loop routes appear because Hello frame propagation fails to keep pace, resulting in a deterioration in the arrival rate.
As a solution to this problem, there is, for example, a method for suppressing the frequency of changes in the route cost CRoute due to changes in the link quality by discretizing link costs which constitute the basis of the route cost CRoute (see Patent Document 1, for example). By suppressing the frequency of changes in the route cost CRoute, route changes are suppressed, and as a result, it becomes possible to suppress the occurrence of loop routes.                Patent Document 1: Japanese National Publication of International Patent Application No. 2010-518745        